Sprinkler head with improved brake and bearing assembly

ABSTRACT

A step-by-step rotary sprinkler head in which the brake mechanism for controlling the arcuate magnitude of the step-bystep movements is manually adjustable by turning a single threaded element to vary the pressure of frictional engagement of a pair of opposed arcuately segmental brake shoes with a ring shaped brake element.

United States Patent 1 11 3,744,720 Meyer July 10, 1973 [54] SPRINKLERHEAD WITH IMPROVED 2,649,268 8/l953 Stein 239/230 BRAKE AND B INGASSEMBLY 586,745 7/1897 Pierce et al..

' 3,187,829 6/1965 Ulinski l88/72.l X [75] Inventor: Larry P. Meyer,East Peoria, [IL [73] g g l fi fi Corporation Primary ExaminerM. HensonWood, Jr.

Assistant ExaminerA. Kashnikow [22] Filed: Mar. 28, 1972 Attorney-JohnW. Malley et al.

[211 Appl. No.: 238,765

7 ABSTRAC [52] US. Cl 239/231, 239/232, 239/233, [5 l T 239/252 188/72",188/83 A step-by-step rotary sprinkler head in which the brake [Sl] Int.Cl B05b 3/08. mechanism for controlling the arcuate magnitude of [58]held of Search "239/230-233 the step-by-step movements is manuallyadjustable by turning a single threaded element to vary the pressure offrictional engagement of a pair of opposed arcuately segmental brakeshoes with a ring shaped brake ele- [56] References Cited mam UNITEDSTATES PATENTS 3,559,887 2/1971 Meyer 239/233 10 Claims, 4 DrawingFigures PATENIEB JUL 0 3. 744; 720

SPRINKLER IIEAD WITH IMPROVED BRAKE AND BEARING ASSEMBLY This inventionrelates to sprinkler heads and more particularly to improvements instep-by-step rotary sprinkler heads.

Step-by-step rotary sprinkler heads are well-known in the art. Sprinklerheads of this type are extensively used in agricultural irrigationsprinkling. All of the sprinkler heads of this type embody a pivotedimpulse arm which is moved through repeated oscillatory cycles duringoperation. The impulse arms are moved through these repeated oscillatorycycles by the engagement of a reactant element on the impulse arm withthe discharge stream of the sprinkler head during each oscillatorycycle. The step-by-step rotary sprinkler heads commonly in use inrelatively low capacity installations effect the step-by-step rotarymovement of the sprinkler head by an impact of the impulse arm with therotary structure of the sprinkler head during each oscillatory cycle ofmovement of the impulse arm. The sprinkler head is provided with afriction brake assembly between the fixed housing structure and rotaryhousing structure of the sprinkler head which serves to control theamount of rotational movement imparted to the rotary sprinkler housingstructure in response to the impact force applied thereto during eachoscillatory cycle of movement of the impulse arm. The higher capacitysprinkler heads of the step-by-step rotary type differ from the lowercapacity types in that the force applied to the rotary housing structureof the sprinkling head during each oscillatory cycle is a streamreactant force rather than an impact force. In the normal operation ofthese higher capacity sprinkler heads, the reactant force applied to therotary housing structure of the sprinkler head during each oscillatorycycle of the impulse arm is relatively high, requiring the provision ofa braking mechanism to control the amount of rotary movement ofconsiderable complexity. Heretofore the braking mechanisms embodied insuch high capacity sprinkler heads have embodied an annular brakeelement which is contacted by an annular brake shoe throughout theannular extent thereof or approximately 360. Conventionally the brakingelement and brake shoe are biased into frictional engagement by aplurality of annularly spaced adjustable spring pressure units. In mostinstances three or more of such adjustable spring pressure units areprovided. In practice, it has been found that the necessity to providefor plural adjustment of the resistance provided by the brakingmechanism has caused some considerable problems. The proper operation ofbraking systems of this type requires that a sub stantially uniformspring pressure be applied by each of the adjustable spring pressureunits. This requirement itself provides considerable inconvenience, somuch so that it is often the case that the spring pressure units are notequally or uniformly adjusted. Where one of the spring pressure units,through carelessness, frustration or the like, remains adjusted to applya greater frictional contact between the cooperating parts of thebraking mechanism than the others, uneven wearing will occur inoperation. Uneven wear can result in a rapidly altering performance,which, in turn, requires further adjustment and the introduction ofpossible further imbalance. The end result is not only considerableinconvenience but reduced performance and sprinkler head life.

Accordingly, it is an object of the present invention to provide astep-by-step rotary sprinkler head of the type described with animproved braking mechanism which has but a single adjusting mechanismfor applying a single uniform spring pressure to the cooperating brakeparts of the mechanism so as to eliminate the inconveniences andproblems noted above.

Still another object of the present invention is the provision of animproved braking mechanism for a step-by-step rotary sprinkler head ofthe type described which embodies an improved bearing assembly.

A still further object of the present invention is the provision of astep-by-step rotary sprinkler head having an improved braking mechanismand bearing assembly which provide the sprinkler head with a highlydesirable overall weight reduction. 5

Still another object of the present invention is the provision of animproved brake mechanism for a stepby-step rotary sprinkler head of thetype described which is simple in construction, efficient in operationand economical to manufacture and maintain.

These and other objects of the present invention will become moreapparent during the course of the follow ing detailed description andappended claims.

The invention may best be understood with reference to the accompanyingdrawings wherein an illustrative embodiment is shown.

In the drawings:

FIG. 1 is a perspective view of a sprinkler head embodying theprinciples of the present invention;

FIG. 2 is a fragmentary elevational view partly in section illustratingthe improved brake mechanism of the present invention;

FIG. 3 is a sectional view taken along the line 33 of FIG. 2; and

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2.

Referring now more particularly to the drawings, there is shown in FIG.1 thereof a sprinkler head, generally indicated at 10, embodying theprinciples of the present invention. The sprinkler head 10 includes afixed housing structure, generally indicated at 12, adapted to befixedly attached to the upper end of a riser pipe or the like (notshown) to which a source of water under pressure is communicated.Journaled in the fixed housing structure 12 for rotation about agenerally vertically extending axis is a rotatable housing structure,generally indicated at 14. The rotatably housing structure includes aninlet portion disposed within the fixed housing structure 12 and anoutlet portion extending thereabove. The outlet portion includes adischarge nozzle 16 at the upper end thereof disposed to direct adischarge stream upwardly and outwardly with respect to the axis ofrotation of the rotary housing structure 14.

Pivotally mounted on the rotatable housing structure 14 is an impulsearm assembly 18 having a reactant element 20 on one end thereof adaptedto engage the stream issuing from the nozzle 16. The engagement of thestream with the reactant element 20 serves to impart successive repeatedoscillatory cycles of movement to the impulse arm 18, the reactantelement 20 also serving to impart to the rotatable housing structure 14,during each oscillatory cycle, an instantaneous force having a componenttangential to the axis of rotation. The sprinkler head 10 also includesa brake mechanism, generally indicated at 22, between the fixed housingstructure and rotary housing structure for controlling the amount ofrotational movement undertaken by the rotatable housing structure inresponse to each instantaneous force applied thereto during eachoscillatory cycle of movement of the impulse arm assembly 18.

The sprinkler head shown in FIG. 1 is of the partcircle type andincludes a reversing mechanism 24 and an adjustable cam assembly 26 foractuating the reversing mechanism 24. The outlet portion of the rotaryhousing structure 14, the discharge nozzle 16, the impulse arm assembly18, reactant element 20, reversing mechanism 24 and cam actuatingmechanism 26 are preferably constructed in accordance with teachings setforth in my earlier commonly-assigned US. Pat. No. 3,559,887 issued Feb.2, 1971. It will be noted, however, that the reversing arm mechanism 24,as shown in FIG. 1, differs somewhat from that of the reversing armmechanism disclosed in my aforesaid patent.

Specifically, the reversing arm is mounted so that the reactant elementon the free end thereof is disposed below the stream when the arm is inits inoperative position and is moved upwardly into the stream ratherthan being moved downwardly into the stream from a position thereabove,as in the aforesaid patent. With this arrangement, the weight of thereversing arm is added to the spring to bias the reversing arm into itsinoperative position. Also, due to the reverse movement of the reversingarm disclosed in FIG. 1, the connecting rod is pivoted to the actuatinglever at a position above the pivotal connection of the lever with thehousing, rather than at a position intermediate this pivotal connectionand the cam roller as in the patented structure.

It will also be noted that since the sprinkler head shown in FIG. 1 isparticularly designed to perform within a capacity range (100 500 GPM)less than that of the sprinkler head disclosed in the aforesaid patent,the rotatable housing has a handle integrally cast therein whichfacilitates manual movement of the sprinkler head from one location toanother.

It will be understood that while the outlet portion of the rotatablehousing structure and the impulse arm assembly 18 pivotally mountedthereon form components of an operable combination of elements to whichthe present invention is applicable, the details of construction ofthese components form no part of the present invention. For purposes ofclearer understanding of the details of construction and function ofthese components, reference may be had to the aforesaid patent, thedisclosure of which is hereby incorporated by reference into the presentspecification.

The present invention is more particularly concerned with improvementsin the brake mechanism 22which cooperate with the action of the impulsearm assembly to control the amount of rotational movement imparted tothe rotatable housing structure 14 in response to the application of theinstantaneous force by the im-' pulse arm assembly 18 during eachoperative cycle thereof. The present invention is also concerned withthe structural and functional interrelationship between the brakemechanism improvements and improvements in the construction andfunctioning of the bearing assembly between the fixed housing structureand the rotatable housing structure.

Referring now more particularly to FIG. 2, the fixed housing structure12 is preferably formed of a pair of upper and lower housing members 28and 30. The

lower member 28 is adapted to be fixedly secured to the upper end of ariser pipe or the like and to this end is provided with internal threads32 within the lower end portion thereof. The lower member 28 includes anannular flange 34 extending outwardly from the upper end portion thereofwhich is adapted to engage the lower end of the upper housing member 30.The lower member is detachably secured in engagement with the uppermember by any suitable means, such as by a plurality of bolts 36 or thelike.

In the preferred embodiment shown, the rotatable housing structure 14 islikewise made up of two rigidly interconnected members 38 and 40 formingthe inlet and outlet portions of the housing structure respectively. Asbest shown in FIG. 2, the lower end of the discharge member 40 isprovided with an annular flange 42 which extends radially outwardlytherefrom. The lower member 38 includes an upper generally rectangularlyshaped attaching flange 44 of a size less than the annular flange 42.The exterior periphery of the lower member 38 is shaped so as to providean upper cylindrical surface 46 extending downwardly from the flange 44and a lower cylindrical surface 48 of a slightly lesser diameter thanthe surface 46 so as to provide a downwardly facing shoulder 50. Theshoulder 50 is adapted to engage the inner race of a ball bearingassembly 52 of conventional construction, the outer race of which ismounted within the upper member 30 of the fixed housing structure.

As shown, the upper member 30 is provided with a main bore 54 of a sizeto receive therein the upper cylindrical surface 46 of the member 38.Preferably, the bore 54 is grooved to receive an O-ring seal 56 whichengages the periphery of the cylindrical surface 46. Formed in the lowerend of the member 30 is a counterbore 58 which forms with the bore 50 aradially inwardly extending flange portion defining a downwardlyextending shoulder which receives the outer race of the ball bearingassembly 52. The ball bearing assembly 52 is retained in operativeposition by any suitable means such as a pair of split rings 60 mountedwithin annular grooves formed within the counterbore 58 and cylindricalsurfaces 48 respectively.

It will also be noted that the lower member 28 includes a radiallyinwardly extending flange portion similar to that provided by the uppermember 30 which receives the lower end portion of the cylindricalsurface 48. Here again, preferably the bore of the flange portion isgrooved to receive a pair of O-ring seals 62 or the like. It can be seenthat the portion of the exterior periphery of the member 38 and theportion of the counterbore 58 extending between the annular O-ring seals56 and 62 defines an annular space which is preferably packed withgrease so as to provide a permanently sealed lifetime lubricated bearingassembly for the sprinkler head 10.

Still referring to FIG. 2, it will be noted that the upper member 30 ofthe fixed housing structure 12 includes an annular wall 64 of anexterior diameter generally equal to the exterior diameter of the flange42, which extends upwardly from the upper end portion of the member 30.The input member 38 and discharge member 40 of the rotatable housingstructure are sealably interconnected by means of a gasket 66 disposedbetween the coextensive portions of the flanges 42 and 44. The flangesand gasket are apertured at annularly spaced locations to receive aplurality of attaching bolts 68. The attaching bolts extend through theregistering apertures in the flanges 42 and 44 and gasket 66 and arethreadedly engaged within an annular mounting member 70 slidably engagedover the cylindrical surface 46 and disposed in a position within theannular wall 64 when the bolts 68 are tightened. Also it will be notedthat when the bolts 68 are tightened, annular flange 42 is disposed inclosely spaced overlying relation with the annular wall 64.

Mounted within the annular wall 64 in surrounding relation with theflange 44 beneath the annular flange 42 is an annular brake element 72preferably in the form of a thin centrally apertured disc. The discbrake element 72 is mounted with respect to the upper member 30 of thefixed housing structure 12 so as to be secured against relativerotational movement with respect thereto but for limited relative axialor longitudinal movement with respect thereto. While any suitable meansmay be provided for effecting this mounting, as best shown in FIG. 3,the annular wall 64 is formed with a plurality of annularly spacedupwardly opening recesses 74, each of the recesses having a pin 76extending upwardly therein. The disc brake element 72 is provided with acorresponding plurality of annularly spaced ears 78 extending outwardlytherefrom which are centrally apertured to receive the pins 76.

The disc brake element 72 forms one cooperating brake element of thebrake mechanism 22, the other cooperating brake elements being in theform of a pair of opposed lower and upper brake shoes 80 and 82. Thelower brake shoe 80, which is of arcuate segmental configuration, isbonded to a backing plate 84 having a pair of apertures formed thereinto receive the upper end of a pair of pins 86 fixed to the member 70below the disc brake element 72.

The upper brake shoe 82, which is of corresponding arcuate segmentalconfiguration, is bonded to a backing plate 88. The backing plate 88with brake shoe 82 bonded thereto is mounted for movement toward andaway from the brake shoe 80 by a threadedly adjustable spring pressuremechanism, generally indicated at 90. While the mechanism 90 may takemany forms, as shown, the brake shoe backing plate 88 has fixed theretoand extending upwardly therefrom a pair of pins 92. The pins 92 extendthrough an apertured boss portion 94 formed integrally above theassociated portion of the annular flange 42, the apertures havingbearings 96 disposed therein for slidably receiving the pins 92.

As best shown in FIG. 4, the mechanism 90 also includes a stud 98threadedly engaged within the boss portion 94 between the bushings 96,the stud 98 extending upwardly and having its upper end threaded toreceive thereon an adjusting nut 100. An equalizer bar 102 having acentral opening 104 therein is engaged over the stud and positioned soas to engage the upper end of both of the pins 92. A coil spring 106 isdisposed over the stud with its lower end in engagement with the the bar102 and its upper end in engagement with adjusting nut 100.

At positions displaced 120 from the stud 98, the flange 42 is providedwith a pair of apertures for receiving the shanks of a pair of buttons108 (see FIG. 3), the heads of which are of a size to extend beneath theflange 42 just out of contact with the upper surface of the disc brakeelement 72, so as to limit the upward axial movement thereof.

It will also be noted that the upper member 30 of the fixed housingstructure 12 is provided with a T-shaped flange 110 which extendsradially outwardly thereof adjacent the lower end of the annular wall64. This flange serves as a means on which the adjustable cam elementsof the reversing mechanism are mounted as will be evident by referenceto the disclosure of my aforesaid patent.

In assembling the present sprinkler head 10, the member is first engagedover the lower end of the member 38 until it is disposed in engagementwith the flange 44. This assembly is then fed downwardly through thebore 54 of the member 30 and the ball bearing assembly 52 is mounted inposition, utilizing the split rings 60. The lower brake shoe bonded tothe backing plate 84 is then positioned on the pins 86, brake element 72is then mounted in position with the apertured ears 78 receiving thepins 76. The discharge member 40 with the adjusting mechanism assembledthereon and the upper brake shoe and backing plate mounted within thebearings 96 and with the buttons 108 disposed within their apertures isengaged over the lower assembly and the assembly is completed bythreadedly engaging the bolts 68 through the apertures in the flanges 42and 44 (with the gasket 66 therebetween) and threaded into the openingsin the member 70.

In this way, the rotatable housing structure 14 is mounted for rotationwithin the fixed housing structure 12 for rotational movement about agenerally vertical axis which is controlled by the frictional engagementof the brake shoes 80 and 82 with the brake element 72. To render thesprinkler head capable of being operatively connected to a riser pipe orthe like, the ball bearing assembly 52 is packed with grease, the lowermember 28 is disposed in engagement with the member 30, and secured inposition by the bolts 36.

When the sprinkler head 10 is mounted in communicating relation with theupper end of a riser pipe and the latter is communicated with the sourceof water under pressure, the water under pressure from the riser pipeenters the member 38, constituting the inlet portion of the rotatablehousing structure 14, and then passes through the member 40 and thenupwardly and outwardly of the discharge nozzle 16. The stream flowingfrom the discharge nozzle 16 engages the reactant element 20 of theimpulse arm assembly 18, causing the latter to undertake repeatedoscillatory cycles of movement as described in detail in my aforesaidpatent. During each cycle of movement, the reaction of the stream on thereactant element 20 creates an instantaneous force having a componenttangential to the axis of rotation of the rotatable housing structure14. Each of these instantaneous forces will effect a rotational movementof the rotatable housing structure 14 of an arcuate extent dependingupon the setting of the adjusting mechanism 90. It will be understoodthat by tightening the adjusting nut a greater frictional contactbetween the brake shoes 80 and 82 and the disc brake element 72 will beaccomplished. Likewise, by loosening the adjusting nut 100 a lesserfrictional contact will be accomplished. The force of the frictionalcontact between the brake shoes and the disc brake element determine thearcuate extent of rotary movement of the rotatable housing structure inresponse to each instantaneous tangential force during each operativecycle of the impulse arm assembly 18. In this way,

the arcuate extent of rotary movement of the sprinkler head can beadjusted with a simple manual turning of a single adjusting mechanism.This arrangement eliminates the need to effect adjustment of a pluralityof adjusting elements and the attendant inconvenience and problemsresulting from the necessity of uniformly adjusting more than oneadjusting element.

It thus will be seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing preferred specific embodiment has been shown and described forthe purpose of illustrating the functional and structural principles ofthis invention and is subject to change without departure from suchprinciples. Therefore, this invention includes all modificationsencompassed within the spirit and scope of the following claims.

I claim:

1. In asprinkler head of the type including a fixed housing structurehaving means thereon for fixedly securing the same to a riser pipe orthe like in communicating relation with a source of water under pressurecommunicated with the riser pipe, a rotatable housing structure havingan inlet portion journaled in said fixed housing structure for rotationabout a generally vertically extending axis and an outlet portionextending above said fixed housing structure, said rotatable housingstructure having interior surfaces for confining water under pressurecommunicating with said fixed housing structure to flow in at least onestream directed upwardly and outwardly therefrom, an impulse armpivotally mounted on said rotatable housing structure for movementthrough repeated oscillatory cycles of operation, means carried by saidimpulse arm engageable with said stream during the operative cyclethereof for effecting repeated operative cycles of said impulse arm andfor imparting to said rotatable housing structure during each operativecycle thereof an instantaneous force having a component tangential tothe axis of rotation of said rotatable housing structure, and brakemeans acting between said housing structures for controlling the amountof rotational movement of said rotatable housing structure in responseto each application of said instantaneous force the improvement whichcomprises said brake means including an annular brake element carried byone of said housing structures in a position with its axis concentricwith the axis of rotation of said rotatable housing structure, brakeshoe means carried by the other of said housing structures in a positionradially outwardly of the axis of rotation of said rotatable housingstructure in frictional engagement with an arcuately segmental portiononly of said annular brake element, said annular brake element beingfree of frictional contact other than by said brake shoe means at saidarcuate segmental portion, spring means operatively associated with saidbrake shoe means for resiliently biasing said brake shoe means intofrictional engagement with said arcuately segmental portion of saidannular brake element with a continuous force, and threadedly adjustablemeans operable by a single manual movement for varying the magnitude ofthe continuous force with which said spring means biases said brake shoemeans into said frictional engagement with the arcuate segmental portionof said annular brake element to thereby vary the rotational movement ofsaid rotatable housing structure in response to the application of saidinstantaneous forces thereto.

2. The improvement as defined in claim 1 wherein said fixed housingstructure includes an annular wall formed at the upper end thereofdisposed in outwardly spaced relation to the adjacent inlet portion ofsaid rotatable housing structure, the adjacent outlet portion of saidrotatable housing structure having an outwardly extending annular flangethereon closely overlying said annular wall, said annular brake elementbeing disposed within said annular wall and below said annular flange.

3. The improvement as defined in claim 2 wherein said annular brakeelement comprises a thin centrally apertured disc having a plurality ofannular spaced integral mounting ears extending radially outwardly fromthe exterior periphery thereof, said annular wall having annular spacedmeans therein engaging said ears so as to prevent rotational movement ofsaid disc about its axis but permitting limited axial movement thereofwith respect to said annular wall.

4. The improvement as defined in claim 3 wherein said rotatable housingstructure includes a brake shoe mounting portion disposed within saidannular wall in spaced relation below said disc, said brake shoe meansincluding a lower brake shoe of friction material carried by said brakeshoe mounting portion with its upper surface in frictional engagementwith the lower surface of an arcuately segmental portion of said disc,and an upper brake shoe of friction material disposed in verticalalignment with said lower brake shoe with its lower surface infrictional engagement with the upper surface of said arcuately segmentalportion of said disc.

5. The improvement as defined in claim 4 wherein said threadedlyadjustable means comprises a stud fixed to said annular flange andextending upwardly therefrom and a nut threadedly engaged on the upperend of said stud, said spring means comprising a helical compressionspring mounted over said stud with its upper end in operative engagementwith said nut and spring pressure transmitting means between the lowerend of said spring and said upper brake shoe.

6. The improvement as defined in claim 5 wherein said spring pressuretransmitting means comprises an equalizer bar having a central openingloosely receiving said stud therethrough and operatively engaging thelower end of said spring, a horizontal plate having its lower surfacebonded to the upper surface of said upper brake shoe, a pair of parallelvertically extending pins fixed at their lower ends to the upper surfaceof said plate and having their upper ends operatively engaged with saidequalizer bar on opposite sides of said stud, said annular flange havinga pair of bearings therein on opposite sides of said stud slidablyreceiving said pins.

7. The improvement as defined in claim 6 wherein said annular wall has aplurality of recesses formed in the upper end thereof of a size toreceive said ears, said annularly spaced ear engaging means comprises apin extending upwardly within each of said recesses, said ears havingapertures formed therein receiving said pins.

8. The improvement as defined in claim 7 including a pair of buttonsdetachably mounted in depending relation to said annular flange atannularly spaced positions with respect to said brake shoes for limitingthe upward axial movement of the adjacent portions of said disc.

thereon and an annular chamber surrounding the exterior periphery ofsaid tubular member between said positions, said annular chamber havinga bearing assembly therein and being packed with grease.

10. The improvement as defined in claim 9 wherein said rotatable housingstructure also includes an exterior tubular member and means fordetachably fixedly securing the lower end of said exterior tubularmember to the upper end of said interior tubular member.

1. In a sprinkler head of the type including a fixed housing structurehaving means thereon for fixedly securing the same to a riser pipe orthe like in communicating relation with a source of water under pressurecommunicated with the riser pipe, a rotatable housing structure havingan inlet portion journaled in said fixed housing structure for rotationabout a generally vertically extending axis and an outlet portionextending above said fixed housing structure, said rotatable housingstructure having interior surfaces for confining water under pressurecommunicating with said fixed housing structure to flow in at least onestream directed upwardly and outwardly therefrom, an impulse armpivotally mounted on said rotatable housing structure for movementthrough repeated oscillatory cycles of operation, means carried by saidimpulse arm engageable with said stream during the operative cyclethereof for effecting repeated operative cycles of said impulse arm andfor imparting to said rotatable housing structure during each operativecycle thereof an instantaneous force having a component tangential tothe axis of rotation of said rotatable housing structure, and brakemeans acting between said housing structures for controlling the amountof rotational movement of said rotatable housing structure in responseto each application of said instantaneous force the improvement whichcomprises said brake means including an annular brake element carried byone of said housing structures in a position with its axis concentricwith the axis of rotation of said rotatable housing structure, brakeshoe means carried by the other of said housing structures in a positionradially outwardly of the axis of rotation of said rotatable housingstructure in frictional engagement with an arcuate segmental portiononly of said annular brake element, said annular brake element beingfree of frictional contact other than by said brake shoe means at saidarcuate segmental portion, spring means operatively associated with saidbrake shoe means for resiliently biasing said brake shoe means intofrictional engagement with said arcuate segmental portion of saidannular brake element with a continuous force, and threadedly adjustablemeans operable by a single manual movement for varying the magnitude ofthe continuous force with which said spring means biases said brake shoemeans into said frictional engagement with the arcuate segmental portionof said annular brake element to thereby vary the rotational movement ofsaid rotatable housing structure in response to the application of saidinstantaneous forces thereto.
 2. The improvement as defined in claim 1wherein said fixed housing structure includes an annular wall formed atthe upper end thereof disposed in outwardly spaced relation to theadjacent inlet portion of said rotatable housing structure, the adjacentoutlet portion of said rotatable housing structure having an outwardlyextending annular flange thereon closely overlying said annular wall,said annular brake element being disposed within said annular wall andbelow said annular flange.
 3. The improvement as defined in claim 2wherein said annular brake element comprises a thin centrally apertureddisc having a plurality of annular spaced integral mounting earsextending radially outwardly from the exterior periphery thereof, saidannular wall having annular spaced means therein engaging said ears soas to prevent rotational movement of said disc about its axis butpermitting limited axial movement thereof with respect to said annularwall.
 4. The improvement as defined in claim 3 wherein said rotatablehousing structure includes a brake shoe mounting portion disposed withinsaid annular wall in spaced relation below said disc, said brake shoemeans including a lower brake shoe of friction material carried by saidbrake shoe mounting portion with its upper surface in frictionalengagement with the lower surface of an arcuate segmental portion ofsaid disc, and an upper brake shoe of friction material disposed invertical alignment with said lower brake shoe with its lower surface infrictional engagement with the upper surface of said arcuate segmentalportion of said disc.
 5. The improvement as defined in claim 4 whereinsaid threadedly adjustable means comprises a stud fixed to said annularflange and extending upwardly therefrom and a nut threadedly engaged onthe upper end of said stud, said spring means comprising a helicalcompression spring mounted over said stud with its upper end inoperative engagement with said nut and spring pressure transmittingmeans between the lower end of said spring and said upper brake shoe. 6.The improvement as defined in claim 5 wherein said spring pressuretransmitting means comprises an equalizer bar having a central openingloosely receiving said stud therethrough and operatively engaging thelower end of said spring, a horizontal plate having its lower surfacebonded to the upper surface of said upper brake shoe, a pair of parallelvertically extending pins fixed at their lower ends to the upper surfaceof said plate and having their upper ends operatively engaged with saidequalizer bar on opposite sides of said stud, said annular flange havinga pair of bearings therein on opposite sides of said stud slidablyreceiving said pins.
 7. The improvement as defined in claim 6 whereinsaid annular wall has a plurality of recesses formed in the upper endthereof of a size to receive said ears, said annularly spaced earengaging means comprises a pin extending upwardly withiN each of saidrecesses, said ears having apertures formed therein receiving said pins.8. The improvement as defined in claim 7 including a pair of buttonsdetachably mounted in depending relation to said annular flange atannularly spaced positions with respect to said brake shoes for limitingthe upward axial movement of the adjacent portions of said disc.
 9. Theimprovement as defined in claim 1 wherein said fixed housing structureincludes a lower annular member having said riser pipe securing means onthe lower portion thereof and an upper annular member detachably fixedlysecured above said lower annular member, said rotatable housingstructure including an interior tubular member disposed substantiallycompletely within said upper and lower annular members, said upper andlower annular members providing interior sealing means engaging theexterior periphery of said tubular member at vertically spaced positionsthereon and an annular chamber surrounding the exterior periphery ofsaid tubular member between said positions, said annular chamber havinga bearing assembly therein and being packed with grease.
 10. Theimprovement as defined in claim 9 wherein said rotatable housingstructure also includes an exterior tubular member and means fordetachably fixedly securing the lower end of said exterior tubularmember to the upper end of said interior tubular member.